German Patent No. 196 06 965 describes a method and a device for controlling the metering of fuel into an internal combustion engine. In the case, a solenoid valve is used as an electrical load in order to control the fuel metering. The temperature of the fuel is inferred on the basis of the resistance of the solenoid-valve coil. The current and the voltage applied to the coil are evaluated for ascertaining the resistance of the coil.
This patent does not take into consideration the energy exchange between the solenoid valve and the surroundings and/or between the solenoid valve and the medium flowing through the solenoid valve.
It is advantageous when, for ascertaining a quantity which is a function of the temperature of the load or which characterizes the temperature of the load, a first filter is used which takes into account the influence of a temperature variable on the quantity, and a second filter is used which takes into account the influence of the current flowing through the load. The procedure is particularly advantageous when ascertaining the coil temperature and/or the coil resistance of a solenoid valve. These variables can be ascertained with little expenditure. Thus, only a few sensor signals are needed which are already partially needed for the control of the load. The ambient air temperature is used in particular as the temperature variable.
A particularly precise simulation of the time behavior of the variables results when the first and/or the second filter has/have at least PT1 behavior.
The quantity, which is a function of the temperature of the load or which characterizes the temperature of the load, is the temperature or the ohmic resistance of the load. In particular, it is the temperature or the ohmic resistance of a coil of a solenoid valve.
A precise simulation of the resistance and/or of the temperature results by taking into consideration the intrinsic heating of the load, which is simulated by the second filtering means. The current flowing through the load is preferably used as the initial basic parameter of the modeling. In this context, the desired current value and/or the measured current value can be utilized.
A particularly advantageous simulation of the behavior of the load, particularly with a view to the possibly energy exchange with the surroundings and/or the medium flowing through the load, results when the first filter includes at least two parallel-connected filters with PT1 behavior, and when the parallel-connected filters have different time behavior. In this context, preferable a measured temperature value for the ambient temperature and/or the temperature of the medium flowing through the load is/are used as initial basic parameter(s) for the modeling.